Method of cleaning a substrate surface using a frozen material

ABSTRACT

In one aspect, the invention includes a method of treating a surface of a substrate. A mixture which comprises at least a frozen first material and liquid second material is provided on the surface and moved relative to the substrate. In another aspect, the invention encompasses a method of treating a plurality of substrates. A treating member is provided proximate a first substrate, and an initial layer of frozen material is formed over a surface of the treating member. A surface of the first substrate is treated by moving at least one of the treating member and the first substrate relative to the other of the treating member and the first substrate. After the surface of the first substrate is treated, the initial layer of frozen material is removed from over the surface of the treating member. The treating member is then provided proximate another substrate, and the surface of the other substrate is treated by moving at least one of the treating member and the second substrate relative to the other of the treating member and the second substrate.

RELATED PATENT DATA

This patent resulted from a divisional application of U.S. patentapplication Ser. No. 09/389,290, which was filed Sep. 2, 1999.

TECHNICAL FIELD

The invention pertains to methods of treating surfaces of substrates,such as, for example, methods of polishing and cleaning substratesurfaces. In particular aspects, the invention pertains to methods ofpolishing and/or cleaning surfaces of semiconductive material wafers.

BACKGROUND OF THE INVENTION

It is frequently desired to treat substrate surfaces during fabricationof semiconductive material wafers. Exemplary processes includeprocedures whereby surfaces of semiconductor substrates are cleanedand/or polished. To aid in interpretation of the claims that follow, theterms “semiconductor substrate” and “semiconductive substrate” aredefined to mean any construction comprising semiconductive material,including, but not limited to, bulk semiconductive materials such as asemiconductive wafer (either alone or in assemblies comprising othermaterials thereon), and semiconductive material layers (either alone orin assemblies comprising other materials). The term “substrate” refersto any supporting structure, including, but not limited to, thesemiconductive substrates described above. An exemplary semiconductivesubstrate is a wafer of monocrystalline silicon.

Among the methods of polishing a semiconductive material surface ischemical-mechanical polishing. Chemical-mechanical polishing isaccomplished by providing a slurry of liquid and solid particulates overa wafer and mechanically abrading the wafer surface with the slurry.(The liquid can comprise, for example, an aqueous solution havingammonium ions therein, and the solid particulates can comprise, forexample, silicon slurry particulates and/or cesium slurry particulates.)The mechanical abrasion can be accomplished by providing a polishing padabove the wafer surface and spinning one or both of the wafer and thepad to cause the wafer surface to be moved relative to the polishingpad. A problem that can occur during polishing of a wafer surface is inremoval of the particulates from over the surface at the termination ofthe polishing process. Particulates that are not removed from over thewafer can cause damage to electrical devices formed over the wafer.

Several procedures have been developed to assist in cleaningparticulates from a wafer surface. Among the procedures is to flush aliquid over the wafer surface while mechanically agitating the liquidwith a cleaning member. Such cleaning member can comprise, for example,a brush or a polishing pad. The agitation of the liquid can help todislodge particles from the wafer surface. Another method which has beenutilized to clean a wafer surface is to project solid particles againstthe wafer surface. In one application, solid particles of carbon dioxide(CO₂) are ejected against a semiconductive material surface to dislodgeparticles from the surface. An advantage of utilizing solid CO₂ is thatthe material can be sublimed from the semiconductive material surface toenable easy removal of the material.

It would be desirable to develop alternative methods for cleaning and/orpolishing substrates. It would be particularly desirable to developalternative methods for polishing and/or cleaning semiconductivematerial substrates, such as, for example, monocrystalline siliconwafers.

SUMMARY OF THE INVENTION

In one aspect, the invention includes a method of treating a surface ofa substrate. A mixture which comprises at least a frozen first materialand a liquid second material is provided on the surface and movedrelative to the substrate.

In another aspect, the invention encompasses a method of treating aplurality of substrates. A treating member is provided proximate a firstsubstrate, and an initial layer of frozen material is formed over asurface of the treating member. A surface of the first substrate istreated by moving at least one of the treating member and the firstsubstrate relative to the other of the treating member and the firstsubstrate. After the surface of the first substrate is treated, theinitial layer of frozen material is removed from over the surface of thetreating member. The treating member is then provided proximate anothersubstrate, and the surface of the other substrate is treated by movingat least one of the treating member and the second substrate relative tothe other of the treating member and the second substrate.

In yet another aspect, the invention encompasses a method of treating asurface of a semiconductive material wafer. A treating member having asubstantially planar surface is provided, and a layer of frozen materialis formed over the substantially planar surface. A surface of asemiconductive material wafer is contacted with the layer of frozenmaterial, and at least one of the treating member and the wafer isremoved relative to the other of the treating member and the wafer.

BRIEF DESCRIPTION OF THE DRAWINGS

Preferred embodiments of the invention are described below withreference to the following accompanying drawings.

FIG. 1 is a diagrammatic view of a substrate surface treatment apparatusencompassed by the present invention.

FIG. 2 is a diagrammatic view of another embodiment substrate surfacetreatment apparatus of the present invention.

FIG. 3 is a diagrammatic view of yet another embodiment surfacetreatment apparatus of the present invention, shown at a preliminarystep prior to providing a substrate proximate the apparatus.

FIG. 4 is a view of the FIG. 3 apparatus, shown at a step subsequent tothat of FIG. 3, and shown having a substrate proximate the apparatus.

FIG. 5 is a view of the FIG. 3 apparatus shown at a step subsequent tothat of FIG. 4.

FIG. 6 is a diagrammatic view of yet another substrate surface treatmentapparatus encompassed by the present invention.

FIG. 7 is a diagrammatic view of yet another substrate surface treatmentapparatus encompassed by the present invention.

FIG. 8 is a diagrammatic view of yet another substrate surface treatmentapparatus encompassed by the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

This disclosure of the invention is submitted in furtherance of theconstitutional purposes of the U.S. Patent Laws “to promote the progressof science and useful arts” (Article 1, Section 8).

The invention encompasses methods of treating substrate surfaces withfrozen solids. In particular embodiments, the invention encompassesmethods of cleaning and/or polishing semiconductive material wafersurfaces, such as, for example, methods of cleaning and/or polishingmonocrystalline silicon wafer surfaces. Several different aspects of theinvention are described below with reference to FIGS. 1-8. In oneaspect, a substrate is cleaned and/or polished by freezing a liquid to asurface of a treating device (such as, for example, a roller or platen)and contacting the substrate to be cleaned or polished with the frozenliquid while applying a mechanical action. After the substrate has beenprocessed, the frozen liquid is mechanically removed, melted orvaporized. A new layer of frozen material can then be reapplied to thetreating device prior to processing another substrate with the treatingdevice. In another aspect, a substrate is sprayed or rinsed with amixture comprising a frozen material and a liquid (of course the mixturecan comprise materials other than the frozen material and the liquid,such as, for example, silicon slurry particles, ammonium ions, and/orcesium slurry particles). In yet another aspect, a substrate issubmerged within a mixture comprising a frozen material and a liquid,and agitated therein. In yet another aspect, the invention encompasses amethod of cleaning and/or polishing wherein frozen particles areinjected into a cold fluid stream which is subsequently flowed directlyonto a substrate.

As will become apparent from the embodiments discussed below, severalaspects of the invention comprise changing materials from one state ofmatter to another, such as, for example, from a solid state of matter toa liquid state of matter. Such phase changes can be accomplished bysubjecting the materials to one or both of a change in temperature or achange in pressure.

A first aspect of the invention is described with reference to FIG. 1,which illustrates a first embodiment cleaning apparatus 10. Apparatus 10comprises a platen 12 having a layer 14 of frozen material formedthereon. Layer 14 can comprise, for example, CO₂, or H₂O, and can beformed by spraying a liquid onto a cooled platen 12. Specifically,platen 12 can be cooled to below a freezing temperature of the materialof layer 14, and layer 14 can be applied to platen 12 as a liquid whichsubsequently freezes to form the frozen layer 14 over platen 12. Anupper surface 15 of layer 14 is referred to as a “treating” surface, assuch will be utilized to treat a substrate surface.

In the shown embodiment, a liquid layer 16 is formed on treating surface15, and accordingly over frozen material layer 14. Liquid layer 16 cancomprise the material of layer 14, or can comprise a different material.Liquid layer 16 can result from surface melting of layer 14, or can beformed by applying a liquid over layer 14. In particular embodiments,layer 16 will comprise a liquid with a lower freezing temperature thanthe material of layer 14 such that the material of layer 16 remains aliquid at temperatures which freeze the material of layer 14. Forinstance, layer 16 can comprise glycol in embodiments wherein layer 14comprises H₂O.

Apparatus 10 further comprises a carrier 18 configured to receive andsupport a substrate. A substrate 20 is shown supported by carrier 18.Substrate 20 can comprise, for example, a semiconductive material wafer,such as, for example, a wafer of monocrystalline silicon. In operation,substrate 20 is lowered to contact one or both of frozen layer 14 andliquid layer 16. Subsequently, at least one of platen 12 and substrate20 is moved relative to the other of platen 12 and substrate 20 to causelayer 14 to move relative to a surface 22 of substrate 20.

In the shown embodiment, cleaning member 12 comprises a substantiallyplanar surface 24 upon which frozen material layer 14 is formed. Also inthe shown embodiment, surface 22 of substrate 20 is substantiallyplanar. Surface 22 has a peripheral edge 26 extending around it. Inparticular applications, substrate 20 is a wafer having a circularshape. In such embodiments, periphery 26 also comprises a circularshape. In the exemplary shown embodiment, planar surface 24 of cleaningmember 12 extends outwardly beyond peripheral 26 on all sides of surface22 of substrate 20. Such enables an entirety of surface 22 to beuniformly polished when wafer 20 is brought into contact with frozenlayer 14 and moved relative to frozen layer 14.

Platen 12 can be referred to as a cleaning member. In particularembodiments of the invention, cleaning member 12 can be replaced withother devices besides a platen, such as, for example, a roller.

It is noted that liquid layer 16 is optional in methods of the presentinvention, but can provide an advantage in removing contaminants fromover frozen surface 14. Specifically, treating member 12 and frozenlayer 14 can together be considered a mechanical treating device whichimparts energy to surface 22 of substrate 20. The rigidity of structures12 and 14 enables such structures to impart significant energy tosurface 22, but such rigid structures are poor for carrying contaminantsaway. Liquid 16, however, has preferred qualities for removingcontaminants from between surface 22 and layer 14. Accordingly, in apreferred application of the present invention, treating member 12 andfrozen layer 14 are utilized to impart energy to surface 22, and fluid16 is flowed across surface 14 to continuously remove contaminants frombetween layer 14 and surface 22.

The method described above with reference to FIG. 1 treats surface 22,and can be utilized, for example, to polish surface 22 and/or to cleanparticulates from surface 22.

After surface 22 has been treated, substrate 20 can be removed fromapparatus 10, and replaced with another substrate which is to betreated. In particular embodiments, treating surface 15 is cleaned priorto providing another substrate within apparatus 10. Such cleaning canremove contaminants from treating surface 15, and accordingly alleviatecross contamination between different wafers treated within apparatus10. The utilization of frozen material 14 can simplify cleaning oftreating surface 15. Specifically, material 14 can be simply melted andremoved from over surface 24 of treating member 12 by, for example,flushing melted material 14 off from surface 12. The melted material 14will carry with it contaminants that had been associated with surface15. Subsequently, a new layer 14 can be frozen on top of treating member12, to form a new, clean, and substantially planar treating surface 15.The melted material of layer 14 can be subjected to a purificationprocess, such as, for example, filtration or distillation, andsubsequently reutilized to form a frozen layer over cleaning member 12.

Of course other methods, besides melting, can be utilized to remove atleast a portion of frozen material 14 from over treating member 12. Suchother methods include, for example, mechanically removing material ofsurface 15 from over member 12, by, for example, scraping or chipping.In particular embodiments, only a thin portion of frozen material 14comprising surface 15 is removed, and the remaining portion of frozenmaterial 14 is utilized in cleaning a subsequent wafer substrate.

Another embodiment of the invention is described with reference to FIG.2. FIG. 2 illustrates an apparatus 30 configured for treating a surface.Apparatus 30 comprises a treating member 32 which, in the shownembodiment, comprises a polishing pad 34. It is to be understood,however, that treating member 32 can comprise other forms, such as, forexample, a brush.

Apparatus 30 further comprises a substrate holder 36, which in the shownembodiment is holding a substrate 38. Substrate 38 can comprise, forexample, a semiconductive material wafer, such as, for example, amonocrystalline silicon wafer. Substrate 38 comprises a surface 40 whichis to be treated. The treatment can comprise, for example, polishingand/or cleaning of surface 40. A mixture of frozen first material 42,and liquid second material 44 is provided on surface 40 of substrate 38.The first material of frozen first material 42 and the second materialof liquid material 44 can comprise the same material. In aspects inwhich the frozen material and liquid material comprise the samematerial, the mixture of materials 42 and 44 can be referred to as aslurry. In one aspect, the frozen material and liquid material can bothcomprise CO₂. In another aspect, the frozen material and liquid materialcan both comprise H₂O. In further aspects, the frozen material andliquid material can both consist essentially of CO₂, or H₂O.

Liquid material 44 can also differ from solid material 42. In aspects inwhich the frozen material and liquid material comprise the differentmaterials, the mixture of materials 42 and 44 can be referred to as asuspension. In such other aspects, the liquid material 44 can comprise alower freezing point than the solid material 42. For instance, solidmaterial 42 can comprise H₂O, and liquid material 44 can compriseglycol. Alternatively, liquid material 44 can comprise a higher freezingpoint than solid material 42. For instance, liquid material 44 cancomprise H₂O and solid material 42 can comprise CO₂.

In embodiments in which liquid material 44 and solid material 42comprise the same material, the mixture of solid material 42 and liquidmaterial 44 can be formed by providing a liquid consisting essentiallyof such material, and cooling the liquid to about a freezing pointtemperature of the material. At such temperature, there will be anequilibrium between a liquid form of the material and a solid form ofthe material.

In embodiments in which the material of liquid 44 differs from thematerial of solid 42, and in which the material of solid 42 has a higherfreezing point than the material of liquid 44, the mixture of solidmaterial 42 and liquid material 44 can be formed by, for example,forming and cooling a liquid blend of the materials that are ultimatelyto be incorporated into solid 42 and liquid 44. Specifically, the liquidblend is cooled to a temperature between the freezing point of thematerial of solid 42 and the freezing point of the material of liquid44. At such temperature, solid 42 will form, and the material of liquid44 will remain liquid. In an exemplary embodiment, the liquid blend willcomprise a blend of liquid H₂O and glycol, and the mixture of solid 42and liquid 44 will be formed by cooling the blend to a temperature belowthe freezing point of water (0° C.) and above the freezing point ofglycol.

Liquid 44 and frozen solid 42 are provided between substrate 38 andtreating member 34. Subsequently, member 34 is utilized to move themixture of materials 44 and 42 relative to surface 40 of substrate 38.Such moving can be accomplished by moving one or both of substrate 38and cleaning member 32. The movement of materials 44 and 42 relative tosurface 40 can cause cleaning and/or polishing of surface 40. Forinstance, pad 34 can be utilized to push the mixture of solids 42 andliquid 44 along surface 40. Solids 42 can be utilized to impartmechanical energy to surface 40 for dislodging contaminants from thesurface, or, in particular applications, for polishing the surface, andliquid 44 can be utilized for flushing the dislodged contaminants awayfrom surface 40.

After the mixture of liquid 44 and solids 42 has been moved relative tosurface 40, such mixture can be removed from the surface. The mixturecan be removed by flushing the mixture off from surface 40 withadditional liquid 44. During or after removal of the mixture fromsurface 40, solids 42 can be melted or sublimed to convert the frozenmaterial from a solid state of matter to another state of matter (i.e.,to a gas if the solid is sublimed, and to a liquid if the solid ismelted). If the solid is melted, a liquid will be formed comprisingmaterials of solids 42 and liquid 44. Such liquid can be a blend ifsolids 42 comprised a different material than that of liquid 44, or cancomprise a single material if solids 42 and liquid 44 comprised commonmaterials. In any event, the liquid formed after melting solids 42 canbe subjected to a purification process, such as, for example, filtrationor distillation. The liquid can then be subjected to conditions whichreform the frozen solids 42 within liquid 44. Such conditions cancomprise, for example, cooling the liquid to a temperature which causesthe material of solids 42 to freeze. After solids 42 are reformed withinliquid 44, the mixture of solids 42 and liquid 44 can be re-utilized toclean and/or polish substrate surfaces.

Another embodiment of the invention is described with reference to FIGS.3-5. Referring to FIG. 3, an apparatus 50 comprises a substrate treatingmember 52 and a substrate holder 54. Substrate cleaning member 52 isshown in the form of a brush, and comprises bristles 56 extending from arotatable member 58. Rotatable member 58 is configured to rotate in adirection indicated by arrow 60 and to accordingly spin bristles 56relative to a substrate held within holder 54.

Referring to FIG. 4, a substrate 62 is provided on holder 54 to besupported by holder 54. Additionally, a layer of frozen material 64 isformed over bristles 56, and cleaning member 52 is subsequentlypositioned proximate substrate 62 such that frozen material 64 contactsa surface 66 of substrate 62. In operation, rotatable member 58 isrotated to spin bristles 56 relative to surface 66 and accordingly tobrush surface 66 with frozen material 64. Contaminants on surface 66 aredisplaced by the mechanical action of frozen material 64, resulting incleaning of surface 66.

Frozen material 64 can comprise, for example, H₂O or CO₂, or can consistessentially of, for example, H₂O or CO₂. Frozen material 64 can beformed by providing a liquid over bristles 56 and subsequently coolingbristles 56 to a temperature below the freezing temperature of theliquid. In one aspect, frozen material 64 can be formed on bristles 56by providing a liquid material over substrate surface 66 (i.e., betweenthe substrate surface and the bristles), cooling the bristles to below afreezing temperature of the liquid, and rotating the bristles to freezethe material onto the bristles.

After surface 66 is cleaned, frozen material 64 can be removed frombristles 56 by melting or subliming material 64, or alternatively byscraping material 64 from bristles 56. In applications wherein material64 is scraped from bristles 56, the material can be subsequently melted.Once material 64 is melted, whether directly melted from bristles 56 orscraped from bristles 56 and subsequently melted, such material can besubjected to a purification process, such as, for example, distillationor filtration, to remove contaminants from the melted material. Thepurified material can then be re-frozen on a cleaning member andutilized again in a process such as that described with reference toFIG. 4. Accordingly, in one aspect of the invention, frozen material 64is utilized to clean a surface of substrate 62 and is subsequentlyconverted from a solid phase to another state of matter. Such otherstate of matter can comprise, for example, a liquid, which issubsequently purified and then converted back to the solid phase to beutilized for cleaning a surface of another substrate.

It is noted that substrate 62 can comprise, for example, asemiconductive material wafer fragment, such as, for example, amonocrystalline silicon wafer. It is also noted that a process of thetype described with reference to FIG. 4 can be utilized to clean a waferafter previous processing steps that form particulates on the wafer. Anexemplary process which would form particulates on the wafer ischemical-mechanical polishing. Accordingly, a process of the presentinvention can be utilized to clean a semiconductive material wafer afterthe wafer has been subjected to chemical-mechanical polishingconditions. Further, in applications in which the methodology describedwith reference to FIGS. 3 and 4 is utilized to clean a plurality ofsubstrates, each of the substrates that is cleaned can be subjected tochemical-mechanical polishing conditions before the cleaning.

A further aspect of the embodiment described with reference to FIGS. 3and 4 is described with reference to FIG. 5. Specifically, FIG. 5 showsthat a second frozen material layer 68 can be formed over first frozenmaterial layer 64. Second layer 68 can comprise the same material asfirst layer 64, or can comprise a different material. An advantage offorming second frozen material layer 68 over first frozen material layer64 is that such can form a clean surface over first frozen materiallayer 64 after the first frozen material layer 64 has been utilized forcleaning a substrate. More specifically, it is recognized that firstfrozen material layer 64 can become contaminated when cleaning asubstrate. Such contaminated first frozen material layer 64 can beundesirable for use in cleaning subsequent substrates, in that thecontamination on first frozen material layer 64 can be transferred tosuch substrates during a cleaning process. One method of addressing suchproblem is to simply remove material 64 and form a new frozen materialover bristles 56. FIG. 5 illustrates an alternative method of addressingthe problem wherein a second frozen layer 68 is formed over first frozenlayer 64, with second frozen material layer 68 effectively forming aclean surface over the surface of first frozen material layer 64. FIG. 5also shows a second substrate 70 held by substrate holder 54. Secondsubstrate 70 has a surface 72 which contacts second frozen materiallayer 68, and which can be cleaned with treatment apparatus 52 byspinning bristles 56 relative to surface 72.

Frozen material 68 can be formed by providing a liquid over first frozenmaterial 64 while cooling first frozen material 64 to a temperaturebelow the freezing temperature of the liquid.

In particular aspects of the invention, a plurality of substrates can becleaned with first frozen material 64, before provision of second frozenmaterial 68. For instance, apparatus 50 can be configured to clean a setof five substrates with first frozen material 64. Subsequently, secondfrozen material 68 can be provided over first frozen material 64 andapparatus 50 utilized to clean another set of five substrates.Accordingly, frozen material is provided over bristles 56 at periodicintervals during treatment of a plurality of substrates. Further, atspecific periods of the cleaning of the substrates, the frozen materialsformed over bristles 56 can be melted from the bristles, and replacedwith a new starting frozen layer, and the process repeated. In theexemplary application described above wherein a new frozen layer isformed at a period corresponding to the treatment of five substrates, anentirety of the frozen layers formed over bristles 56 could be meltedfrom the bristles after every 25 wafers, and a fresh buildup of frozenmaterials initiated over the bristles. Further, the frozen materialsremoved from the bristles could be melted and purified, and subsequentlyre-frozen on the bristles.

Although the treating member 52 described above with reference to FIGS.3-5 is described as a brush, it is to be understood that such treatingmember could comprise other forms, such as, for example, a pad.Preferably, the frozen materials described above with reference to FIGS.3-5 are formed at portions of the treating member which contact asurface of a substrate which is to be cleaned. Accordingly, if thetreating member is a pad, the frozen materials will be probably beformed at a surface of the pad which enables the frozen materials tocontact a surface which is to be cleaned.

In further aspects of the invention described above with reference toFIGS. 3-5, the frozen materials formed over the bristles of cleaningmember 52 can be at least partially melted as such bristles are movedrelative to a substrate. In such applications, the frozen materialundergoes a phase-change from a frozen state of matter to a liquid stateof matter during a cleaning process. Such can be advantageous forflushing contaminants from a surface of a substrate during cleaning withthe cleaning member 52.

Although the removal of frozen material from over cleaning member 52 isdescribed with reference to FIGS. 3-5 as comprising melting or scrapingon the material, it is to be understood that in other embodiments thefrozen material can be removed by subliming the material. In such otherembodiments, contaminants released from the sublimed material can becollected prior to utilizing cleaning member 52 on subsequentsubstrates.

The embodiment described with reference to FIGS. 3-5 utilized a cleaningmember 52 to clean only one of two opposing surfaces of substrate 70.FIG. 6 shows an apparatus similar to that described with reference toFIGS. 3-5, but configured to clean a pair of opposing surfaces ofsubstrate 70. The apparatus of FIG. 6 is shown at a processing stepsimilar to that of FIG. 5, and numbering identical to that utilized indescribing FIG. 5 is used for FIG. 6. A difference between the FIG. 6apparatus and that of FIG. 5 is that substrate holder 54 (FIG. 5) is notvisible in the FIG. 6 embodiment. If the substrate holder 54 of FIG. 5were utilized in the apparatus of FIG. 6, such could block one of thecleaning members from contacting a surface of the substrate. Instead ofsuch substrate holder, the FIG. 6 apparatus can utilize, for example, asubstrate holder that retains substrate 70 at its edges (not shown).

Another embodiment of the present invention is described with referenceto FIG. 7, wherein a cleaning apparatus 100 is illustrated. Cleaningapparatus 100 comprises a substrate holder 102, which is illustratedholding a substrate 104. Substrate 104 can comprise, for example, asemiconductive material wafer, such as, for example, a wafer ofmonocrystalline silicon.

Apparatus 100 further comprises a liquid/solid ejection system 110.System 110 comprises a first tube 112 having an inlet 114 and an outlet116. A liquid 118 is flowed into tube 112 through inlet 114, and out oftube 110 through outlet 116. Outlet 116 is smaller than inlet 114.Accordingly, liquid flows out of outlet 116 at a greater pressure thanit flows into inlet 114. The higher pressure liquid is ejected onto asurface 105 of substrate 104 to clean such surface.

Device 110 further comprises a second tube 120 having an inlet 122 andan outlet 124. Tube 120 flows through a chamber 126 configured toconvert a liquid-state material to a solid-state material. Chamber 126can comprise, for example, a region wherein one or both of a temperatureand a pressure of a flowing liquid is changed to convert the flowingliquid to a flowing plurality of frozen particles.

A liquid 130 flows into tube 120 and through chamber 126, and isconverted to solid particles 132. Solid particles 132 are preferablyrelatively fine particles, and can be referred to as a “snow”. Solidparticles 132 are dispersed within the liquid 118 flowing through tube112, and are accordingly ejected from outlet 116 with liquid 118.

The ejected solid particles and liquid can clean surface 105. The solidparticles can provide mechanical force against substrate surface 105which displaces contaminants from substrate surface 105, and the liquid118 flowing across surface 105 can sweep the displaced contaminants offof the surface.

In particular applications, liquid 118 and solid particles 132 compriseCO₂. Accordingly, the liquid and solid convert to a gas upon warming ofsubstrate 104 to room temperature. In other embodiments, liquid 118 andsolid 132 can both comprise H₂O. In yet other embodiments, liquid 118can comprise a different material than that of solid 132. For instance,liquid 118 can comprise glycol and solid 132 can comprise H₂O. Asanother example, liquid 118 can comprise water and solid 132 cancomprise CO₂. In one aspect, liquid 118 and frozen particles 132 can bereferred to as a mixture flowed out of tube 112 and across surface 105of substrate 104.

Although frozen particles 132 are described as being formed with achamber 126, other methods of forming frozen particles are encompassedby the present invention. For instance a method of forming the frozenparticles within a liquid, instead of utilizing chamber 126, is toutilize a second liquid 130 which freezes at a higher temperature thanfirst liquid 118. First liquid 118 is cooled to below the freezingtemperature of second liquid 130, and second liquid 130 is injecteddirectly into the cooled first liquid 118 whereupon the second liquidfreezes to form particulates of frozen material. Exemplary liquids forutilization in this aspect of the invention are glycol and H₂O, whereinthe H₂O freezes at a higher temperature than does glycol.

The apparatus of FIG. 7 moves a mixture of frozen and liquid materialrelative to a substrate surface by flowing the mixture across thesubstrate surface. FIG. 8 illustrates an aspect of the present inventionwherein a similar effect is accomplished by submerging a substrate 150within a mixture 160 of frozen and liquid materials (the frozen andliquid materials of mixture 160 can be the same as those described abovewith reference to FIG. 7), and agitating the mixture. Such agitation canrub frozen material across surfaces of the substrate to clean suchsurfaces. Substrate 150 can comprise, for example, a semiconductivematerial wafer. The agitation can be accomplished by, for example,stirring the mixture and/or moving substrate 150. Although substrate 150is shown resting on the bottom of a vessel in FIG. 8, it is to beunderstood that substrate 150 could be supported off of the bottom ofthe vessel with a holder (not shown).

It is noted that among the advantages of utilizing frozen materials forcleaning in accordance with the present invention is that surfaceproperties of such materials can be changed with chemical or thermalmodifications. Accordingly, a surface of a frozen material can be madesofter, or harder, for particular applications by modifying one or bothof a temperature of the frozen material surface or a chemicalcomposition of the surface.

In compliance with the statute, the invention has been described inlanguage more or less specific as to structural and methodical features.It is to be understood, however, that the invention is not limited tothe specific features shown and described, since the means hereindisclosed comprise preferred forms of putting the invention into effect.The invention is, therefore, claimed in any of its forms ormodifications within the proper scope of the appended claimsappropriately interpreted in accordance with the doctrine ofequivalents.

What is claimed is:
 1. A method of treating a plurality of substrates, comprising: providing a treating member proximate a first substrate; forming an initial layer of frozen material over a surface of the treating member; treating a surface of the first substrate by moving the treating member having the initial layer of frozen material thereon relative to the surface of the first substrate; after treating the surface of the first substrate, removing the initial layer of frozen material from over the surface of the treating member; after removing the initial layer of frozen material, providing the treating member proximate an other substrate; treating a surface of the other substrate by moving the treating member relative to the surface of said other substrate; wherein a plurality of additional substrates are provided, the additional substrates having surfaces which are treated with the treating member after the surface of the first substrate is treated and before the surface of said other substrate is treated, the initial layer of frozen material remaining over a surface of the treating member during the treating of the surfaces of said plurality of additional substrates: and wherein one or more additional layers of frozen material are formed over the initial layer of frozen material after the surface of the first substrate is treated and before at least some of the surfaces of said additional substrates are treated.
 2. A method of treating a plurality of substrates, comprising: providing a treating member proximate a first substrate; forming an initial layer of frozen material over a surface of the treating member; treating a surface of the first substrate by moving the treating member having the initial layer of frozen material thereon relative to the surface of the first substrate; after treating the surface of the first substrate, removing the initial layer of frozen material from over the surface of the treating member; after removing the initial layer of frozen material, providing the treating member proximate an other substrate; treating a surface of the other substrate by moving the treating member relative to the surface of said other substrate; wherein the initial layer of frozen material is formed over the treating member by providing liquid material between the first substrate and the treating member and subsequently freezing the material onto a surface of the treating member; and wherein the freezing occurs during or after the moving of the treating member relative to the first substrate.
 3. A method of treating a plurality of substrates, comprising: providing a treating member proximate a first substrate; forming an initial layer of frozen material over a surface of the treating member; treating a surface of the first substrate by moving the treating member having the initial layer of frozen material thereon relative to the surface of the first substrate; after treating the surface of the first substrate, removing the initial layer of frozen material from over the surface of the treating member; after removing the initial layer of frozen material, providing the treating member proximate an other substrate; treating a surface of the other substrate by moving the treating member relative to the surface of said other substrate; and wherein the removing the initial layer of frozen material comprises scraping the material from the surface of the treating member.
 4. A method of treating a plurality of substrates, comprising: providing a treating member proximate a first substrate; forming an initial layer of frozen material over a surface of the treating member; treating a surface of the first substrate by moving the treating member having the initial layer of frozen material thereon relative to the surface of the first substrate; after treating the surface of the first substrate, removing the initial layer of frozen material from over the surface of the treating member; after removing the initial layer of frozen material, providing the treating member proximate an other substrate; treating a surface of the other substrate by moving the treating member relative to the surface of said other substrate; and the method further comprising: melting the initial layer of frozen material, subjecting the melted material to purification conditions; and re-freezing the material onto the treating member before treating the other substrate.
 5. The method of claim 4 wherein the melting occurs during the removing of the material from the treating member.
 6. The method of claim 4 wherein the melting occurs after the removing of the material from the treating member.
 7. The method of claim 4 wherein the melted initial layer of frozen first material is filtered before it is re-frozen.
 8. A method of treating a plurality of substrates, comprising: providing a treating member proximate a first substrate; forming an initial layer of frozen material over a surface of the treating member; treating a surface of the first substrate by moving the treating member having the initial layer of frozen material thereon relative to the surface of the first substrate; after treating the surface of the first substrate, removing the initial layer of frozen material from over the surface of the treating member; after removing the initial layer of frozen material, providing the treating member proximate an other substrate; treating a surface of the other substrate by moving the treating member relative to the surface of said other substrate; and wherein the initial layer of frozen material comprises CO₂.
 9. A method of treating a plurality of substrates, comprising: providing a first material between a surface of a treating member and a surface of a first substrate, at least some of the first material being in a form of a first state of matter; after providing the first material, moving the treating member relative to the surface of the first substrate; changing the form of at least some of the first material from the first state of matter to a second state of matter; while the at least some of the first material is in the form of the second state of matter, subjecting the first material to a purification process; after the purification process, changing the form of at least some of the first material from the second state of matter back to the first state of matter; after changing the form of at least some of the first material back to the first state of matter, providing the treating member proximate a second substrate and providing at least some of the first material that has been changed back to the first state of matter between the second substrate and the treating member; and moving the treating member relative to the surface of the second substrate.
 10. The method of claim 9 wherein the phase change of the first material from the first state of matter to the second state of matter is accomplished by subjecting the first material to one or both of a change in temperature and a change in pressure.
 11. The method of claim 9 wherein the phase change of the first material from the second state of matter to the first state of matter is accomplished by subjecting the first material to one or both of a change in temperature and a change in pressure.
 12. The method of claim 9 wherein the first state of matter is solid and wherein the solid first material is provided between the surface of the first substrate and the surface of the treating member as a slurry in a liquid first material.
 13. The method of claim 9 wherein the first state of matter is solid, and wherein the solid first material is provided between the surface of the first substrate and the surface of the treating member as a suspension in a liquid second material.
 14. The method of claim 13 further comprising forming the suspension, the forming the suspension comprising: providing a liquid mixture of first material and second material, the first material having a higher freezing point than the second material; and cooling the liquid mixture to a temperature which freezes the first material while leaving the second material as a liquid.
 15. The method of claim 13 wherein the first material comprises H₂O and the second material comprises glycol.
 16. The method of claim 13 wherein the first material comprises CO₂ and the second material comprises H₂O.
 17. The method of claim 9 wherein the first state of matter is solid and the second state of matter is liquid.
 18. The method of claim 9 wherein the first material comprises CO₂.
 19. The method of claim 9 wherein the first material comprises H₂O.
 20. The method of claim 9 wherein the first material comprises CO₂, and wherein the first state of matter is solid and the second state of matter is liquid.
 21. The method of claim 9 wherein the first material comprises H₂O, and wherein the first state of matter is solid and the second state of matter is liquid.
 22. The method of claim 9 wherein the treating member comprises a brush or a pad. 